Lubricants and antioxidants therefor



United States Patent Office 3,3615% Patented Jan. 2, 1958 3,361,675)LUBRICANTS AND ANTIGXIDANTS THEREFQR Bruce W. Hotter], Orinda, Calih,assignor to Chevron Research Company, San Francisco, Calif., acorporation of Delaware N Drawing. Filed Sept. 20, 1965, Ser. No.488,780 Claims. (Cl. 252-421) This invention relates to greasecompositions and as antioxidant additives therefor, novel polyarylureas. More particularly, it relates to greases which are thickened bymetal-soap type thickeners which tend to promote oxidation, thesegreases being inhibited from oxidation by the polyaryl polyureas.

Lubricants which are employed in present-day machinery, such asautomobiles, etc., are becoming increasingly subject to attack byoxidation due to the severe operating conditions encountered in themachines. In particular, the increased speeds, pressures, andcorrespondingly high temperatures at which the machines are operatedproduce these results. The consequences of oxidative attack, a buildupin oxidative products in the lubricant and a loss in lubricity result inincreasing Wear upon parts being lubricated and often in early failureof the equipment.

The aforementioned effects of oxidation are particularly pronounced inthe case of greases, and, more specifically in the case of greases whichare thickened by metal ion-containing substances, such as soaps, etc. Amost particular case in point are the greases which are gelled bylithium soaps. These greases are most often employed in high temperatureapplications, due to their extremely high dropping points. Thus, thecombination of high temperature and the presence of metallic ion in thecompositions subjects the lubricant base to extreme conditions ofoxidation. Many conventional anti-oxidants are ineffective in theseapplications. For example, phenolic and sulfur-containing antioxidantswhich are often used to inhibit oxidation in lubricating oils are oflittle effectiveness in these compositions. While diaryl amines havebeen used in inhibiting metal-containing greases, and they are effectiveantioxidants, they are usually quite toxic and are often corrosive tocopper parts with which the grease is contacted.

It has now been found that metallic-soap thickened grease compositions,highly resistant to oxidation and greatly reducing wear of lubricatedsurfaces, result from the inclusion in said composition of a minoramount of a polyaryl polyurea of the formula:

wherein n is 3 to 8; R R and R are hydrocarbyl radicals of 1 to 24carbon atoms; and x, y and z are 0 to 1. Thus, the antioxidant compoundsof this invention are ring-substituted aryl carbamido derivatives of acompound having alternate methylene and phenylene radicals in achain-like structure. Thus, the compounds may be prepared by reacting asuitable amine with a ring-substituted pol-yisocyanate or by reacting anisocyanate wlth a polyamine in which the amino groups are on a suitablepoly- (phenylmethylene) chain. It is preferred that there be from about3 to 8 phenylene groups in the chain.

The additives of this invention are most conveniently prepared by thereaction of aniline or hydrocarbyl-substituted aniline with apoly(phenylmethyleneisocyanate). An example of a suitable and preferredisocyanate is a material designated poly(alkylphenyl) polyisocyanate, orPAPI, sold by the Carwin Company is a material having an average of 4 to5 phenylmethylene groups per molecule. The amines which are reacted withthe isocyanate are aryl amines, either unsubstituted or substiuted onthe rings by hydrocarbyl groups of from 1 to 24 carbon atoms.Illustrative materials are aniline, and various alkyl-substituedanilines, such as methyl, ethyl, propyl, dodecyl, tridecyl, etc.anilines. An example of preferred material is dodecyl aniline. Alsosuitable are polyalkylsubstitued analines such as dimethylaniline,di(dodecyl) aniline, etc.

The polyaryl polyureas are prepared by reacting the isocyanates andamines. This reaction can be effected by simply mixing the materialstogether; however, heating will speed the reaction. The materials arereacted in such proportions that at least one amine group is present foreach isocyanate group. Thus, molar ratios of from about 3 to 1 up toabout 8 to 1 are employed.

The materials are employed in the grease compositions in amountssufiicient to inhibit oxidation. Amounts of from 0.01% to 5% by weightare preferred. Examples of the grease thickeners which are employed inthe compositions of this invention include the metallic soaps which areusually the salts of saturated fatty acids containing more than 10carbon atoms (stearic, palmitic, lauric, etc.) and the salts of oleicacid, an unsaturated fatty acid. The metallic ions which are employedinclude aluminum, barium, cadmium, calcium, chromium, cobalt, copper,iron, lead, magnesium, manganese, mercury, nickel, silver, strontium,thallium, tin, and zinc. The materials which are especially useful inthe compositions of this invention are the soaps of lithium, oftenemployed because the soaps are high melting and are thus useful in hightemperature application, and where susceptibility to oxidation becomesquite important. An example of a highly useful soap is a lithiumstearate soap.

The oleaginous lubricants which comprise the bases for the compositionsof this invention are those oily or greasy materials most commonlyemployed in lubrication. Examples of these materials are natural andsynthetic oils and greases made from these oils. Base materials whichare not suitable for the compositions of this invention and are notclassified as oleaginous lubricants are those inorganic substancessometimes used in lubrieating functions, such as molybdenum disulfide,tungsten disulfide, graphite, ground glass, ground basalt, etc.

The oils which can be used as base oils for the compositions of thisinvention include a Wide variety of luricating oils, such asnaphthenic-base, paraffin-base and mixed-base lubricating oils, otherhydrocarbon lubricants, e. g., lubricating oils derived from coalproducts, and synthetic oils, e.g., alkylene polymers (such as polymersof propylene, butylene, etc., and the mixtures thereof), alkyleneoxide-type polymers (e.g., alkylene oxide polymers prepared bypolymerizing alkylene oxide, e.g., propylene oxide polymers, etc., inthe presence of water or alcohols, e.g., ethyl alcohol), carboxylic acidesters (e.g., those which were prepared by esterifying such carboxylicacids as adipic acid, azelaic acid, suberic acid, sebacic acid,alkenylsuccinic acid, fumaric acid, maleic acid, etc., with the alcoholssuch as butyl alcohol, hexyl alcohol, 2-ethylhexy1 alcohol,pentaaerythritol, etc.), liquid esters of acids of phosphorus,alkylbenzenes, polyphenyls (e.g., biphenyls and terphenyls),alkylbiphenyl ethers, polymers of silicon, e.g., tetraethyl silicate,tetraisopropyl a silicate, tetra(4-methyl-2-tetraethyl) silicate,hexyl(4- methyl-Z-pentoxy) disiloxane, poly(methyl) siloxane, andpoly(methylphenyl) siloxane, etc.

The base oils can be used individually or in combinations, whenevermiscible or wherever made so by use of mutual solvents.

The following examples illustrate the preparation of In addition to thesubject inhibitors described in this application, the lubricatingcompositions of this invention may also contain other lubricating oiland grease additives, such as oiliness agents, extreme pressure agents,oxidation inhibitors, rust inhibitors, corrosion inhibitors, viscosityindex improving agents, dyes, lubricating oil detergents, etc.

the polyurea antioxidants of this invention. The examples are onlyillustrative and are non-limiting.

Example 1 A 65 g. portion (0.5 equivalent) ofpoly(phenylmethyleneisocyanate) having an average of four to fivephenylmethylene units was mixed at room temperature with 131 g. (0.5mol) of dodecylaniline. An exothermic reaction resulted, and thematerial was heated with mixing to 180 C. and held for 60 minutes untilcompleted. The resultant product was 184 g. of a resinous materialhaving a melt- TABLE I Concentra- Bomb Bearing Life Antioxidant Additivetion, Weight Oxidation, (Geometric Mean) Percent p.s.i. drop None 27 53;236; 376 (170). Zinc dibutyltlliocarbamat 2 -3. 3 196; 76 (132).Plwnyl-anaphthylamlnm 2 (79 Polyarylpolyurea 2 1,183; 746 (940).

I claim: I. A polyarylpolyurea of the formula: H cH. H

NHGQNH ing temperature in the range of 130 to 160 C.

In order to demonstrate the effectiveness of the compounds of thisinvention in reducing oxidation of a grease and increasing bearing lifeof bearings lubricated by the grease, greases containing smallquantities of the material were subjected to a bomb oxidation test and ahearing life test.

The mob oxidation test, ASTM D-942-50, briefly involves placing a 20 g.sample of the grease in a bomb, and subjecting the sample to an initialpressure of 110 p.s.i. of oxygen at 200 F. for 100 hours and thenmeasuring the pressure loss at the end of the period. In general, thehigher absorption of oxygen indicates greater oxidation of the sample.

The bearing life test used is known as the Navy High Speed Bearing Testand is described in Federal Test Method No. 331.1. In this test, a ballhearing was operated at 10,000 r.p.rn. continuously for approximately 22hours at 300 F. while being lubricated with the subject grease sample.The apparatus was then cooled to room temperature during a period of twohours. This procedure of operating and cooling was repeated until therewas hearing failure. The number of hours to bearing failure is indicatedas Bearing Life.

The table following shows the results of the abovementioned test. Thebase grease was a synthetic oil (bis- 2-ethylhexyl sebacate) thickenedwith 15% by weight of a lithium stearate soap. The Bearing Life for eachsample and the geometric mean of the Bearing Life are given. Comparativedata for an uninhibited grease and greases inhibited with conventionalantioxidants, zinc dithiocarbamate and phenyl-a-naphthylamine, areincluded (see Table I).

As noted from these data, the zinc dibutylthiocarbamate actually gave alower bearing life than uninhibited grease, and the polyaryl polyurea ofthis invention gave a Bearing Life significantly higher than either thethiocarbamate or the phenyl-ix-naphthylamine, which, as previouslymentioned, is a highly toxic material.

In addition to the particular usefulness of the polyarylureas asoxidation inhibitors in greases, they are also useful as antioxidants inother lubricants such as in lubricating oils used in machinery andautomotive applications. Examples of such oils are those previouslydescribed as suitable bases for the greases of this invention.

wherein n is 3 to 8; R R and R are hydrocarbyl radicals of l to 24carbon atoms and x, y, and z are 0 to 1.

2. The polyarylpolyurea of claim 1, wherein n is 4 to 5 and R R and Rare alkyl groups.

3. The polyarylpolyurea of claim 2, wherein x is 1, y and z are 0.

4. The polyarylpolyurea of claim 3, wherein R is an alkyl group of 6 to20 carbon atoms.

5. The polyarylpolyurea of claim 4, wherein R is a dodecyl group.

6. A lubricating composition comprising an oleaginous lubricant base andin an amount sufiicient to inhibit oxidation a polyarylpolyurea of theformula:

wherein n is 3 to 8; R R and R are hydrocarbyl radicals of 1 to 24carbon atoms and x, y, and z are 0 to 1.

7. The composition of claim 6, wherein R R and R are alkyl groups.

8. The composition of claim 7, wherein x is 1 and y and z are 0 and R isan alkyl group of 6 to 20 carbon atoms.

9. The composition of claim 6, in which the oleaginous lubricant base isa metal soap thickened grease.

10. The composition of claim 9, in which the grease is a lithium soapthickened grease.

References Cited UNITED STATES PATENTS 7/1954 Hill et al. -a 25251.55/1959 Katz 26O77.5

6. A LUBRICATING COMPOSITION COMPRISING AN OLEAGINOUS LUBRICANT BASE ANDIN AN AMOUNT SUFFICIENT TO INHIBIT OXIDATION A POLYARYLPOLYUREA OF THEFORMULA: H-((((R3)X-((R2)Y,(R1)X-PHENYLENE)-NH-CO-NH)-1,3-PHENYLENE)-CH2)N-H WHEREIN N IS 3 TO 8; R1, R2 AND R3 ARE HYDROCARBYL RADICALS OF1 TO 24 CARBON ATOMS AND X, Y, AND Z ARE 0 TO
 1. 9. THE COMPOSITION OFCLAIM 6, IN WHICH THE OLEAGINOUS LUBRICANT BASE IS A METAL SOAPTHICKENED GREASE.
 10. THE COMPOSITION OF CLAIM 9, IN WHICH THE GREASE ISA LITHIUM SOAP THICKENED GREASE.